Apply transforms to all other keyframes
In the screenshot you have multiple object selected. 
You can select all keys in a frame when you select only the armature (Armature.001), then there will be a yellow dot in the Dope Sheet Summary line.


Right click ( RMB) to select this keyframe
&#9096; CtrlC
Select the destination frame ( LMB)
&#9096; CtrlV (paste) 


Or in one step:


Select keyframe ( RMB)
Duplicate and move with &#8679; ShiftD